Running: Your Guide to Hydration & Dehydration

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Running: Your Guide to Hydration & Dehydration

Ensuring we maintain a good level of hydration has been proven to enhance performance whilst exercising. The muscles and brain require a certain minimum of water and salt for strong and healthy performance.

About DehydrationHow Much to Drink?What to Drink?Electrolyte DrinksElectrolyte GelsFurther Suggestions


Dehydration is a condition that occurs when someone loses more fluids than the body is taking in. Hydration is crucially important for anyone of any age.

Our bodies are about two thirds water. When we become dehydrated, it means the amount of water in the body has dropped below the level needed for normal body function. The key factors in dehydration are not only water, but electrolytes, which our bodies lose through sweat during exercise. The main electrolyte is sodium, which is a salt our body naturally produces. We do however rely on other body salts - the body rapidly loses potassium and magnesium through perspiration when we exercise. It is essential we then replace these as quickly as possible to avoid severe dehydration.

What happens when we are dehydrated?

Dehydration will have a direct and negative impact on the body, causing fatigue during earlier stages of exercise. Usually if we are feeling thirsty, that already means we have become dehydrated. As our body becomes dehydrated our blood volume decreases, making it harder for blood to return to our heart. So consequently the less oxygen-rich our blood is reaching our muscles, the more fatigued we become, making it near impossible to maintain a good level of anaerobic exercise.


Knowing how much you need to drink per hour of exercise is the challenging bit. Research suggests that we need between 300-800ml of liquid per hour, depending on conditions and the individual. That is a large margin of difference, so how to narrow it down?

Firstly, trust your thirst. Then consider the weather. Aim for 300ml in moderate temperatures and 400ml in hotter conditions, but carry more so you can increase if you feel the need. Experiment, write down how much you drink and how you feel in the 24 hours after your run. Check your urine immediately after your run and the next day. Then adjust what you drink next run. If you write down the results you won't be struggling to remember and you will establish exactly what works for you.

The key factors of dehydration are obviously what our bodies lose through perspiration. Sweating during exercise is healthy and perfectly normal! So there is no need to worry, however each individual will have a different sweat rate. This can easily be monitored and calculated by taking your body weight before and after a run or race.

For example, if you lost three pounds during a training run, you would need to drink about 4.5 pounds of fluid (4.5 pints) over the next several hours to be sure that you are fully rehydrated. How much fluid to take on board is also something many of us are often confused about. This is also a very personal part of your regime and again will depend our sweat rate. Sweat rate tends to be the most important factor, but also the conditions, duration, and time of the event will have a major influence on how much fluid we need to consume.

Monitoring what our intake should be will depend on our fluid losses from training and other activities. If we replace less fluid then we have lost each day, then obviously our hydration levels will not be right. The easiest way of monitoring our body's hydration level is to analyse urine colour and quantity. If it is darker and more concentrated, that means you are dehydrated; a paler and less concentrated urine will mean that your body is well hydrated. This is a fantastic guideline leading up to a race, so even the night before you will be able to have a good indication of what your hydration levels are like.


The key to staying hydrated is not only fluid intake, but also intake of electrolytes – the minerals we lose through sweating. This is especially important when running long distances.

The 3 main key electrolytes are Sodium, Potassium, and Magnesium. These all help the body to function properly. Having an electrolyte-based drink or gel with a high content of these three minerals will aid the body's recovery, and should be comfortably absorbed and digested.

There are essentially two ways to handle this: either with electrolyte drinks, or with a combination of electrolyte gels and plain water. This is down to personal preference, as either will do the job. If you're training for anything from a marathon upwards, it is always a good idea to have tried a couple of alternatives beforehand, to see what your stomach prefers.

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Runner drinking


If you don’t use gels then mix your water with electrolyte-rich energy sources. When running in high temperatures you can add hydration tablets to your water and also consume gels for more of an electrolyte boost. Electrolyte drinks tend only to have a content of salt and very low sugar – if any – making them ideal to drink before during and after a race.

Maurten Drink Mix 160 Sachet

Precision Hydration Effervescent Electrolyte Tablets


If you experience stomach cramps, a feeling of indigestion, or like your stomach is uncomfortable from being full of water, then drinking less is not necessarily the solution, especially if you feel light headed when you cut down water consumption. Instead you need to increase the sodium going into your body. Personally this is my experience on hot, long runs. A combination of Elete add-in in my water plus electrolyte-rich gels has solved the problem. When I run with two bottles one contains Elete and the other Active Root to settle my stomach. Maurten is also a great option as it features seaweed extract for easy absorption and does not upset the digestion process.

Active Root Single Sachet (1 x 35g)

Elete Electrolyte Add-In 25ml

Maurten Drink Mix 160 Sachet


These quench your thirst, absorb faster than water and supply a little bit of energy.

Tailwind Nutrition Endurance Fuel 2 Servings

High 5 Zero

SIS Go Electrolyte Powder 500g


Isotonic drinks absorb at the same rate as water, quench your thirst and also give you an energy boost. They are a good alternative to just plain water as they contain between 6-8 grams of carbohydrates in every 100ml. They also contain salt which allows the body to use the fluid efficiently. These would be an ideal sports drink for a 5k, 10k and half-marathon runner. An example is SIS Go. Tailwind appears here again as you can alter the amount of water you mix it with.

Tailwind Nutrition Endurance Fuel Caffeinated 2 Servings

Maurten Drink Mix 160 Sachet


If you choose this option, just make sure you’re consuming enough gels to hit the electrolyte balance; just one gel on a 90 minute run is not going to work. Gels supply you with energy as well as electrolytes. If you are consuming good quality gels (see below for my recommendations) every half hour or so and sipping water regularly you only need to experiment with how much water you need – as laid out above.

Maurten Gel 100

Maurten Gel 100 Caf 100


Hydration package when you’ve only got access to water, like during a race.

Carry some salt chews (they taste fine) plus whichever gels you like best of these sodium packed options. 

SaltStick Fastchews

Lucho Dillitos Guava Paste

Energy Gel

Energy Gel

Hydration package for your training runs

Choose one solution for your water bottle and supplement with some gels for additional energy. If using Maurten only combine with Maurten Gels as that will be the simplest for your body to digest. 

Tailwind Nutrition Endurance Fuel 2 Servings

Elete Electrolyte Add-In 25ml

Maurten Drink Mix 320 Sachet

Maurten Gel 100 Caf 100

How to carry water on your runs

After using a waist belt for many years, I’m now a Race Vest convert and I love it! You have space for all the gels you need, your phone, your energy bar (for those long, long runs) and two bottles packed full of hydration. I put Active Root in one and Elete Add-in in the other.

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Salomon Sense Pro 2 Set

Montane Gecko VP 5+ 2023

Salomon Adv Skin 12 Set

Women's Salomon Adv Skin 12 W Set

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